ethanol & 2-strokes

pbool

Senior Member
Joined
Apr 6, 2005
Messages
174
Location
leaf river, Illinois
Aircraft
bensen B8M & pitbull
Total Flight Time
since 1968
Does anyone out there know if ethanol can safely be used in 2 cycle engines? The station I have always bought my gyro gas at has today gone to ethanol. I have a 6 gallon can mixed up because I didn't notice the new sticker until the deed was done. I don't have any other engines to try it out on so if anyone has any info I would appreciate hearing it. John M
 
Hi John

I not 100% sure of the problem but I think it has to do with the oil not liking the alcohol and not mixing will, at any rate DON'T USE IT, i'm sure others can give you a more accurate reason.

Tony
 
Service information detailing the use of automotive fuel in the ROTAX two cycle aircraft engine provides the following warning, 'Oxygenates (alcohol additives) are to be avoided, any volume over 5% cannot be used. Testing for alcohol (content) is the only safe way to be sure your fuel is o.k. for use in your ROTAX.'
 
Al, You test every time you buy gas? How do you test for the presents of alcohol? What brand and octane gas do you buy? Thanks, stuart
 
I believe you can test for the presence of alcohol in gas by filling a tall skinny container 1/4th full with water and marking the level carefully . Then fill the rest of the way with the test gas. Shake it up and recheck the water level. If it raises (because the alcohol in the test gas mixed with the water) the test gas has alcohol in it. The mixture must then be discarded. I'll test this out tonight because I need to mix up some gas myself.

Edit: Just came back from Gasahol 101. I used a skinny salad dressing bottle for the test. If you use good gas with the water they separate rather quickly with the water and gas both clear. The same test with gasahol first forms a third layer that's milky then it finally makes a cloudy mixture on the bottom with the level raised about 10% like it should. The gas also became somewhat cloudier after the test.
The Amoco station i used for the "good" gas test also gave me a system status report that read out how much of each type of gas there was in their tanks along with the quantity and depth of water in the bottom.
 
Last edited:
These are the answers I figured would come up. I was in a snowmobile shop last winter and saw a kit for sale that was used to check for the presence of alcohol. I figured there must be a reason for it. A farmer I know claims most vehemently that it is fine for 2 strokes, but then he sells the corn that makes the stuff. I think I will search out another source for gas. The stuff I mixed up will see service in my lawn mowers. Thanx for the quick replies.John M
 
Fuels Containing Alcohol

Some stations sell fuels containing alcohol such as ethanol. These ingredients should be avoided since they create all kinds of problems including, in 2-stroke engines, the absorption of water into the alcohol, which then creates corrosion, and the reduction of the oil's lubricating properties. Rotax recommends avoiding fuels containing more than 5% alcohol.
\

Stuart, no I never tested for alcohol when I was running a Rotax 618, but I did always get gas from the same place and same brand, which was known to be ok by the other pilots in the area. I did check for water in the gas and drained the sump before flight.
Never had a fuel problem, but my friend has had two engne outs over the swamp, ending in rollovers, in his gyro, so far, both from fuel problems; as in fuel starvation.
 
I tried out the test myself using a rain gauge tube which already has markings on it. When I tested the gas that already had the oil in it, it took a while for the mixture to clear and separate. I put in 1 inch of water and added 2 more inches of gas. After the shakeup and clearing, the water had gained a quarter of an inch. This gas is going into the lawn mowers. I bought another 6 gallons from another station which has no labels stating that it contains alcohol. I tested it before adding oil and it separated almost instantly and showed virtually no gain in the water level. At least I still have a source for gas that is only a few more miles away. John M
 
KenSandyEggo said:
I always use the taste-test myself.
Hello Ken, I am not familiar with the taste test. How is it done? Thank you, Vance
 
Pbool
I put that in my chainsaw once and it desolved all the neoprine parts in the carb. Orings, Diaphram. :(
JMTC
Sonny
 
Last edited:
One good rule of thumb concerning two strokes is ANYTHING added to your gas that is not gas will lean your mixture! Yes even adding extra oil can cause a lean mixture and burn a hole in your piston! The alcohol family does the same thing! :eek:
 
Oh boy! I'm dreading making this post, but here goes.

Some of you may know that I'm still chasing a problem with high egt readings on my 447.

I just read Phil's post and gess what? I've been running a little extra oil in my mix. I use the Penzoil for air cooled engines as recomended by Rotax. Each quart is supposed to be mixed with 6 gallons of gas to make a 50:1 ratio. Well my gas cans are 5 gallons and I was just too lazy to measure and figured that a little extra oil might foul my plugs sooner but that it certainly wouldn't "hurt" my engine. I had even discusssed this with a few others and was told to just keep doing what I'm doing. You know - err on the rich side.

So if Phil's theory is correct, maybe this is causing a "leaner" fuel mixture and giving me the high temps. Obviously, I can check by mixing correctly which I will. Can I get more opinions from the "experienced ones" about this?
 
Rick I disagree. I don't think the little bit of extra oil is " leaning " your mixture. You can try getting 6 gallon jugs and trying it, or a measuring cup and using the right amount of oil for 5 gallons, but again I highly doubt you will see any measureable difference.

Btw I have a bunch of 5 gallon jugs and I can usually get closer to 5 and a half or a tad more gas in them without overflowing the jug....
 
The problem with Corngas - ethanol - and two stroke engines is the oil does not like to mix as well the that type of fuel and more importantly is the fact that the alcohol absorbs moisture and holds it in, so you end up with rusting problems on the bearings and other steel parts inside the engine.

I would try to avoid it if possible, and one alternative fuel you can always count on if all the gas in your area is corngas is to buy Avgas at your local airport. That gas is the same no matter where you go in the country and it is clean and burns well. The lead deposits may cause a need for decarboning the pistons and ring grooves a tad earlier than you might have to if you only ran unleaded gas, but at least you know your getting good fuel.

93 Octance car gas is averaging 2 dollars and 35 cents a gallon here and avgas at a few local airports is as low as 2 dollars and 70 cents a gallon, so it isn't that much more right now.
 
Any other opinions regarding too much oil in the mix creating a "lean" fuel mix which might cause higher EGT readings?

Phil, tell me more. In your experience, should my proportions cause a problem?
 
Fuel/air ratio has to do with how much fuel gets sucked through a little hole (main Jet) for a givin amount of suck (air). Oil is much thicker than gas, so in my opinion it would be harder to suck through the little hole. The suck doesn't change. The question becomes "is the range of variance we are talking about enough to cause a problem?" I don't know the answer.

When we switched from castor based oil to diester based oils (synthetic) we had to change several jet sizes.

It has been my experance that exhaust gas tempeture from one engine to another is not consistant enough to make jetting decisions, but we were running engines much closer to the edge in road racing motorcycles. Even slight variances in the exhaust port or exhaust pipe can cause a large difference in tempeture seen on the gage. A small change in the location of the sender can also change what the gage says.

On a somewhat related note, Calvin Rayborn, a well known Harley factory road racer, was killed on a Suzuki two stroke running on alcohol. We felt at the time that the oil wasn't mixing well (Castrol) and the jetting wasn't just rite. In Road Racing, two strokes seize going in to the turn as you are back shifting because the throttle is shut, cutting off the oil. This is not that different than chopping the throttle for a simulated engine out landing. Thank you, Vance
 
Last edited:
Top